change usb_cam_python.fix nsize.

src/driver/driver_camera_ioctl/usb_cam_python.cpp

@@ -302,7 +302,7 @@ int StopCam(char * strvideoname)
 {
     std::string strvideo = strvideoname;
 
-    int nsize;
+    int nsize =gvectorthreadcam.size();
     int i;
     iv::threadcam * pthreadcam = NULL;
     int index;